Answer: You would only apply grub prevention products if you are having a problem with grubs damaging your lawn. If you need to control grubs, beneficial nematodes can be applied now in late summer to early fall. Your local Cornell cooperative extension should also have information available on grub control, but here is the information from their web site about grubs and grub control.
With red maples grown from seed, there will be some natural variation between the bloom performance from tree to tree, so some are just better bloomers than others. However, if one of the trees seems stressed and is growing less vigorously overall, you would need to try to figure out why. It might be growing in a spot that is drier than the others, or where it is contacted by winter deicing salts from a road, or where there is limited space for the roots, or it may be overcrowded and shaded by nearby trees for example. These types of limitations can be difficult to change.
If you want to give it a boost and see if that helps, you could spread a thin layer of good quality compost over the root area of the tree. The roots will spread out well beyond the branch tips.
I hope this helps!
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